A variety of devices exist for handling large rolls of wound web, such as rolls of photosensitive paper and film, during web manufacturing operations. For photosensitive roll products, this operation is generally conducted in the absence of light. With the advent of worldwide supply chains, the core used, even on large rolls of wound web, is normally a paperboard tube. These paperboard tubes are expendable at the end user site, so there is no need for a return system. While the economics of this type of core are generally favorable, the core, nonetheless, presents problems. Significantly, experience indicates that the paperboard cores of the rolls of wound web can be quite easily damaged if the chucks that engage them for handling and transport arc not precisely centered in core openings.
A typical example of this type of roll handling situation arises where the roll is unwound, by for instance winder/unwinder equipment, such as described in U.S. Pat. No. 5,308,217, issued May 3, 1994, by Pienta, and entitled, "Roll Chucking Apparatus," and then exposed to further independent treatment. Experience indicates that it is more practical to handle rolls of web on the outer surface as opposed to a center core. In order to unwind the roll of web with even tension control, however, the roll is best supported by the core of the roll. The core of the roll is supported by the core openings on opposing ends of the roll.
Engagement of chucks or pins into core openings of the core using some sort of circumferential surface support device has always been a problem because the outer diameters of the cores are not the same from roll to roll, or even from side to side on one roll. Additionally, there is winding side shift and equipment positioning tolerances to account for. Moreover, the exact location of the core openings is quite variable.
As the chucking device enters the hollow core openings, the inner layers of paperboard can shear off and cause binding as they rotate or fold about the core. Furthermore, the paperboard can wedge between the inner wall of the core and chucking device. This happens even when the chucking device has smoothly tapered or round edges for entering the core of rolls that can weigh in the thousands of pounds.
An existing practice for aligning a roll with a chucking device is to first introduce the roll to a pre-alignment station in a well-lighted environment prior to the intended alignment. In this case, the roll is aligned with pseudo-chucks that are located in the same relative position as the real intended machine chucks. This usually involves an operator visually inspecting each side of the roll, and determining which way to incrementally move the roll, until both of the pseudo chucks can be freely inserted into the core. Generally the roll has a core end that is typically cone-shaped, and not positioned perpendicular to the machine centerline. This requires the roll to be manuvered into several planes. The roll is then moved into the intended chucking position without disturbing the roll attitude, other than a horizontal translation from the pre-alignment position to the operating position. At that point, the roll is chucked into engagement, using full power equipment usually on a large turret, in process conditions (which may well be dark) and within range of other powerful and dangerous automatic start and splice equipment. It is normal manufacturing practice to splice the tail of one roll to the start of the next, for continuous web supply to the downstream processing systems. This presents a confined and dangerous situation for an operator to see how to jog the roll into alignment, hence the pre-alignment station.
Conventional equipment for transporting the roll of web to a chucking station uses multiple powered drives that can rotate, tip, side-shift, raise-lower, and move forward-reverse in order to provide the flexible motion needed to position the roll accurately. It is well known that this practice is quite expensive, slow, space consuming, and, depending on the operator accuracy, generally unreliable.
Another problem with existing devices for handling rolls of web for chucking arises when the chuck device is withdrawn from the core openings of the roll core and damage results to the core. This can occur even if the chucks complete their full engagement stroke. The onset of this problem may arise if the core is slightly damaged sufficient enough to cause severe wedging of paper inside the core. The chucks can be very difficult to remove in this case and sometimes their failure to cleanly withdraw from the core may cause a complete shutdown of the whole operation. When this occurs, skilled operators are required to disengage the chuck from the core.
Yet another problem with presently available devices for handling a roll of web prior to chucking is that there exists no known feasible way to provide the space required for a pre-alignment station, discussed above.
Moreover, skilled artisans will appreciate that the alignment of large rolls has several interrelated motions, where time, space, cost, and complexity all have boundaries that prevent simply adding all the equipment required to provide for all necessary controlled motions.
It is well known in the prior art to use load cells on a lift that is supporting the roll, to detect if the chucks were pushing up or down too hard on the core. A major shortcoming of this approach, however, is that there is no recognition of horizontal forces, axial forces, or combinations of opposing vertical forces. This may occur where there is force applied by the chuck on one end of the core that forces the core upwardly; and, simultaneously, a force is applied to the opposing end of the core that forces the core downwardly. The load cell may detect a zero sum change although both ends of the core may have been damaged as a result of the forces.
Removing a roll from the chucks has also been a problem where the roll is somewhat cone-shaped. Traditionally, if the roll is even slightly cone-shaped and the lift fixed in a horizontal plane for simplicity, it is almost impossible to unload the weight from the chucks evenly, which must be accomplished if the chucks are to be retracted without damage to the core.
Notwithstanding the aforementioned problems in the art, there has been some success partially aligning a roll of web with respect to a mounting position of a chucking device. For instance, in U.S. Pat. No. 5,192,033, titled "Apparatus for Moving Rolls From a Loading Station to an Unwinding Station and for Moving Empty Roll Cores From the Unwinding Station to the Loading Station," to Pipes, an apparatus is disclosed for moving rolls from a loading station to an unwinding station and for moving empty roll cores from the unwinding station to the loading station. Pipes provides for separate lifts positioned on each end of the core, which correct for a taper wound roll, but uses the core to measure with. Further, U.S. Pat. No. 5,308,217 discloses a roll chucking apparatus that operates based on forces being applied to the roll being transported and is capable of only a vertical corrective positioning of the roll.
However, both of the aforementioned prior art patents only provide for vertical positioning capability of the roll to be chucked relative to the chuck position. These prior art teachings, therefore, each fail to provide flexible, multi-directional, orienting, and aligning movements of the roll of web to a chuck.
Therefore, a need persists in the art for an apparatus for handling rolls of web that can provide flexible vertical and translational movements for precise docking with a chuck device. Moreover a need persists for a system for transferring a wound roll of web from an exterior surface support station, to a center core support element of independent, cooperating equipment, and back to the surface support as required by the manufacturing system without producing any damage to the roll.